The purpose of this project is to determine the speed and accuracy with which human observers recognize spatial and temporal patterns of visual stimulation. Four sub-areas of work are concerned with (a) a cross-correlation that is apparently responsible for detecting displacements of complex random-dot displays; (b) sensitivity to the velocity, acceleration, and other spatio-temporal changes of a single, continuously moving spot of light; (c) the phenomenon of shape constancy, or the speed and accuracy for obtaining information that is invariant under projective transformation; and (d) the specific deficiency of retarded readers in recognizing stationary visual patterns. The general objective is to determine both the specific geometric properties that are more easily recognized and the processes that account for performance.